I just weighed between getting an R3A and an M3. They're pretty much the same price, if you get a user M3 on eBay (but you could end up having to pay for a CLA as well). After fiddling with an R3A, I went with the M3. The main reason was that the shutter of the Bessa is louder and shakes the camera. I already have a Bessa T, so this time I was looking for a really smooth shutter. It had to be the Leica. I bought one from a sophisticated seller than vouched for the accuracy of the shutter and viewfinder.
If you use glasses, the M3 finder, which has slightly less magnification, gives a better view of the 50mm frameline.